Proper connecting rod torque

[Chris R]

Anyone have any idea/recommendations for the proper value to torque the falcone rod bolts to?

The manual tells you not to reuse them but doesn't give any values. I have been told 25 ftlbs but the value comes without known provenance.

I will probably torque the old bolts I have to their limit to confirm but it would be nice to know what people do.

I gather that properly torqued loctite/peening the nuts is not required.

The airone bolts look identical, are they?

Thanks,

Chris

[pehayes]

I did not know this answer myself. I asked another knowledgeable person who does not frequent this list. His answer is:

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I have always put rod bolts on when fitting the rollers at 28 lb ft. I believe I calculated what the value should be when I measured the size of the rod bolts and considered the bolt temper characteristics.

The other thing is that when you grind the crank and fit new rulli, the rod has to be honed to fit with just the slightest amount of drag. Sammy Hale and I did this with at least 4 Guzzi crankshafts. We torqued the new bolts at 28 lb ft. You always have to go back to the same torque as you had when doing the fitting, or binding will occur due to the rod cap going out of round. And Guzzi rods are very sensitive to this. Rod bolts and caps have to be put on exactly how they were when honed and the rod bolts are very precise. The rulli have to pass two cracks....

If I were fitting new rulli without honing the rod or grinding the crank, I would start out at about 20 lb ft. Then I would work it up to 28 lb ft gradually and not go further. However, if binding occurs earlier, you might have to relax the torque a little to achieve the proper drag. I wouldn't do this personally. It is easy enough to get someone to hone the rod to fit new rulli properly.

I have about a dozen new rod bolts on hand for the Falcone. They cost me $12.50 each and I'll sell them for that to Guzzisti. I have no idea if they fit an Airone and I don't know of any that are apart right now to measure.

Using loctite 680 on the nuts during final assembly of the rod bolts is highly recommended. The Guzzi factory has always staked the bolt/nut joint on assembly, but they didn't have loctite back then.
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Can you identify the part number for the Airone rod bolts? I'll match that to the Falcone number to see if they are the same.

Patrick Hayes
Fremont CA

[Chris R]

Thanks Patrick.
Arggh! I just bought some at great expense from Stucchi - the price actually wasn't too outrageous but the shipping was. You don't have a front chain drive cog do you?

Funny my guess was that the proper stretch for a bolt of that width and length and material to be around 3 thou based on most other bolts I have encountered - which works out on a oil/moly lubricated bolt to be around 28ft/lbs! This is done after torquing and untorquing the bolt three times which as I learned at CAT school is the proper way to do it. As you infer the most prudent thing would be to resize the rods whenever you take them apart as god knows what guzzi actually fitted them at and it is comparatively cheap. Also the rods don't have any dowels which make them susceptible to distortion as you point out. Given that they look fine and seem to work fine and I don't want to disturb the case hardening I will blue them and just do a final check that the 'Rulli' are rolling evenly.

Loctite now do a high temperature/high strength loctite -2620 - that is probably the best stuff if one feels the need. I have assembled hundreds of engines from tiny two strokes to ginourmous diesels and never used loctite or staked the rod bolts and never had a rod failure that wasn't caused by extreme abuse/very old age. I am a bit torn as to whether it is really necessary - either way the bolts are single use.

I have a falcone so I am not really concerned about interchangeability with the Airone except that they look identical and I was curious.

Ta,

Chris

[lucky phil]

Considering the crude nature of the Falcone rod (no locating dowels and highly sensitive to misalignment) and the educated guess over bolt torque why not just order a carrillo rod for it.They will make a custom rod to whatever size you require and considering what you are getting aren't outrageously expensive either.Carrillo rod bolts are reusable as well withing sensible limits.
Ciao

[Chris R]

That is not a bad suggestion - Carillo make excellent rods. Indeed they are almost too beautiful to hide inside an engine!

I went to the factory with the late great Carroll Smith when it was still owned by Mr. Carillo. After a long chat with him about Italy, Guzzi's and what not he went into the back and handed me a pair of rods for my lemans gratis!

Ta,

Chris